This invention relates generally to cable assemblies and more particularly has reference to a push-pull cable conduit formed of material which changes color to indicate imminent failure due to exposure to excessive heat.
Pertinent U.S. and foreign patents are found in Class 73, subclass 356; Class 74, subclasses 501 P and Digest 10; Class 116, subclasses 206, 208 and 216; Class 136, subclasses 36 and 125 and Class 528, subclass 335 of the official classifications of patents in the U.S. Patent and Trademark Office.
Examples of the most pertinent U.S. patents are U.S. Pat. Nos. 3,581,523, 3,416,389, 3,528,312, 3,373,632, 3,516,299, 3,320,665.
The patents show push-pull cables formed of plastic material. However, none of the patents discloses a self-indicating push-pull cable that changes jacket color when failure due to excessive heat is imminent.
Push-pull cables are often used in high temperature environments. Many attempts have been made to produce cable conduits capable of withstanding high temperature, but none has been completely successful. All known cable conduits fail after long use at high temperature.
Unexpected or untimely failure of the cable conduit is a serious problem because it causes excessive down time for the machinery in which the cable is used. Because it is easy to replace a cable assembly before failure during normal maintenance, persons skilled in the art have long sought an apparatus or method for predicting a cable failure of the assembly. However, the problem of unexpected cable failure due to exposure to excessive heat has heretofore remained unsolved.